Scanning Our Skeletons: Bone Images Show Wear and Tear

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Scanning Our Skeletons: Bone Images Show Wear and Tear

What can you learn from 80 million x-rays? The secrets of aging, among other things. Sharmila Majumdar, a radiologist at UC San Francisco, is using an arsenal of computer tomography scans to understand how our bones wear out from the inside.

It works like this: A CT scanner takes superhigh-resolution x-rays of a bone, then combines those individual images into a three-dimensional structure. The results are incredibly detailed; a scan of a single segment of bone can run 30 gigs.

Majumdar's method is to churn through the data to identify patterns in how the trabeculae — the material inside bone — changes in people who have diseases like osteoporosis and arthritis. In one day of imaging, it's not uncommon for the lab to generate nearly a terabyte of data. Researchers also aggregate the data from many subjects, putting hundreds of terabytes to work. Majumdar hopes to learn why some patients suffer severe bone loss but others don't. "We don't know the mechanism of bone loss," she notes. "Once we learn that, we can create therapies to address it."

How to Look Inside Our BonesThis slice of a human hip joint is 82 microns thick — about half the width of a human hair. Other machines used by the lab can go as fine as 6 microns — the size of a human red blood cell. Each bone is scanned about 1,000 times, creating, in this case, a clear look at osteoporosis in action.

Using image processing, the slices are combined into a 3-D model, creating a picture of what the bone looks like from the outside ...

... and from the inside. This image of a human vertebra shows the internal microstructure of bone, called the trabeculae.

The lab then analyzes the model for weaknesses in density and strength. In this image, the thicker structures are color-coded green, while thinner material is colored red. Majumdar's lab combines hundreds of models to detect bone-loss patterns that help us understand how humans age.